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Direct Address Multi-Tap Transformer

IP.com Disclosure Number: IPCOM000049420D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Goodrich, RA: AUTHOR

Abstract

Transformers used for resistance welders require various turn ratios between the primary and secondary sides to provide various volt-ampere outputs to the welding electrodes. In the past, switching of the turn ratios was done with contact-type switches. Because of this, to reduce or prevent arcing, switching took place at no load. This introduced interruptions in the welding process, and thus was not only time consuming but inferior welds resulted.

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Direct Address Multi-Tap Transformer

Transformers used for resistance welders require various turn ratios between the primary and secondary sides to provide various volt-ampere outputs to the welding electrodes. In the past, switching of the turn ratios was done with contact-type switches. Because of this, to reduce or prevent arcing, switching took place at no load. This introduced interruptions in the welding process, and thus was not only time consuming but inferior welds resulted.

In process control required by changing conditions such as supply line variations, phase shifting or cycle time can be effected by the electronic transformer tap switches (Figs. 1 and 2). In a synchronous timer arrangement a weld schedule is programmed whereby at each half cycle an address is applied to inputs 20 to selectively turn on or off ignitrons 40 (Fig. 1) or silicon-controlled rectifiers (SCRs) 50 (Fig. 2) to control weld current in the secondary 60 and in turn through electrodes 70 and load components 80. With this direct-address control it is possible to satisfy different requirements of various applications, such as applications where there are two or more thicknesses of materials to be joined together.

Further, it may be desirable to have a low transformer tap output for pre-heat or post-heat and a high transformer tap output for welding or a transformer tap output change between welds. Thus, the present arrangement can provide the necessary control for changing weld cu...